Ecosystems on Long Time Scales

Introduction

• The speaker is currently at the University of Washington.

• He has published numerous papers and received funding from the National Science Foundation (NSF).

• He expresses gratitude for the opportunity to present the seminar and appreciation for the students.

Overview of the Talk

• The talk will blend ecology, plant biology, and earth science/geology.

• It emphasizes the need for skill sets from both areas to interpret ecosystems on long time scales.

• The presentation will cover some of the speaker's newer, ongoing research projects.

• Feedback and insights from the audience are welcomed.

Vegetation Change Through Time

• The speaker presents a fossil palm example to illustrate vegetation changes over time.

• The fossil is from the Swauk Formation, east of the Cascades.

• Vegetation changes primarily in response to climate, but other factors also play a role.

• The talk will explore the speaker's research following the path of the Yellowstone Hotspot.

• The research aims to compare rates of change in different vegetation communities.

• Local fossil collection efforts in Pierce County will also be briefly discussed.

Central Oregon: Present vs. Past

• Central Oregon today is a dry landscape with pines, sage rock, and grasslands.

• In contrast, 16 million years ago, Central Oregon was a wet taxodium swamp with hardwoods.

• It was inhabited by North American camels, rhinos, and bone-crushing dogs.

Vegetation Change on Recent Time Scales

• 20,000 years ago, the South Sound area was under ice.

• 15,000 years ago, it was a recently deglaciated landscape with ice-marginal tundra or sagebrush steps.

• Today, the South Sound, exemplified by the Ohop Valley, is densely vegetated with Douglas fir and riparian vegetation.

Research Focus: Interplay Between Climate and Vegetation

• The speaker's research focuses on understanding the interplay between climate and vegetation.

Studying Past Vegetation: The Role of Lakes

• Lakes are excellent repositories of environmental information.

• They collect environmental debris, especially pollen, which is crucial for understanding past vegetation.

• Macrofossils and fossil charcoal found in lake sediments provide additional insights.

• Cores from modern lakes allow the recovery of pollen from sediment layers.

Pollen Analysis

• Pollen from various plants, especially those using airborne pollination, is studied.

• The sediment layers provide a record of how ecosystems changed over time.

• Fossil charcoal indicates the frequency of landscape burning.

• Cores from modern lakes help recover pollen from sediment, showing plant life over thousands of years.

Fieldwork and Data Recovery

• Fieldwork involves recovering sediment from ancient lakebeds to study pollen.

• The goal is to understand how different plant communities have changed over time.

• Multivariate data, including relative abundances of pollen types, are analyzed to reconstruct past ecosystems.

Application of Knowledge: Short-Term Ecosystem Change

• Research focuses on understanding short-term ecosystem changes, particularly during the Miocene Climatic Optimum (17-14 million years ago).

• This period is significant because Earth's climate was as warm as it is projected to be in the next 100 years.

• The research aims to understand how ecosystems behaved during this period.

Factors Driving Rapid Change

• Climate variability: Hyperthermals (periods of very warm conditions) occurred about every 100,000 years during the Miocene Climatic Optimum.

• Frequent volcanic disturbance: Concurrent with climate variability, there was intense volcanic activity in the Northwest.

• Columbia River flood basalts erupted, and the Yellowstone hotspot began tracking across the region, causing large volcanic eruptions.

Fossil Floras in the Northwest

• Numerous fossil floras from the Miocene Climatic Optimum are found in Washington, Oregon, and Idaho.

• The research focuses on three specific sites: Sucker Creek, the Mascall Formation, and Clarkia.

Sucker Creek

• Located along US 95, near Marsing, Idaho.

• Characterized by small lakes that existed for no more than 30,000 years each.

• Rich in fossil remains, including leaves, fish, pollen, and some vertebrates like elephants.

• Diverse pollen assemblage includes conifers (Douglas firs, hemlocks), hardwoods (sweet gum, elm), and podocarps (which no longer grow in North America).

Diversity within Sucker Creek

• Cool temperate hardwood forests with unusual conifers.

• Mixed forests with both hardwoods and conifers living in close association.

• Herbaceous assemblages indicating open landscapes, possibly grasslands.

• Herbaceous pollen, often found after volcanic eruptions, indicates significant secondary succession following disturbances.

Mascall Formation

• Older than Sucker Creek, dating back about 16 million years.

• Characterized by larger lakes and thick deposits of lake sediments like diatomites and lignites.

• Pollen samples are scarce, but notable for the abundance of elm pollen.

• Vertebrate fossils are more common than plant fossils.

• One sample provides evidence of a genuine grassland, possibly influenced by the rain shadow effect of the Cascades.

Clarkia

• Known as Lagerstätten due to exceptional fossil preservation.

• Fossil leaves can be lifted from rocks, sometimes retaining original coloring.

• A project is underway to test for DNA fragments in these fossils that are 16,000,000 years old.

• Again, a very large lake with a long record existed here.

Vegetation in Clarkia

• Diverse pollen assemblage with conifers, hardwoods, and herbaceous plants.

• Chiefly hardwood forest dominated by chestnut and oaks, surrounded by taxodium (cypress) swamps.

• The vegetation remained relatively stable, even through volcanic eruptions.

Comparison of Fossil Sites

• Sucker Creek: Discontinuous lakes, variable composition, frequent volcanic disturbance.

• Mascall Formation: Discontinuous, varied between grasslands and elm forests.

• Clarkia: Continuous, less varied, suggesting stable forest composition.

The Challenge of Comparing Vegetation Records

• Comparing vegetation records from different sites presents a challenge due to the variety of plant assemblages.

• The goal is to understand when changes were dramatic and how quickly ecosystems changed.

• The question is whether rates of change are intrinsic to plant migration and tolerance or influenced by unique conditions in a warmer world.

Rate of Change Approach

• The approach involves reducing multivariate data to a metric of dissimilarity.

• It addresses the statistical challenge that observations in time series data are not independent.

• 
  Data are binned into 3,000-year intervals.

• Dissimilarity metrics are used to plot data.

• The rate at which the dissimilarity metric changes is calculated.

Application to Younger Settings

• Similar approaches have been used for more recent time scales. For example: the last 18,000 years.

• Studies analyze large pollen datasets to identify periods of rapid vegetation change.

• One study used 1,200 pollen datasets to study vegetation changes over the last 20,000 years in North America.

• The arrows are pointing to areas where you had really rapid ecosystem change going on: approximately thirteen thousand years ago. What's going on like thirteen thousand years ago? What are the earth science students doing? We're coming out of the last ice age.

Time Scales

• The last piece: the need to pull time in if you are gonna calculate a rate of anything, you need to have some sense of time.

• 
  Classic reasons to be unable to do this is needing radiocarbon age models, running around in the background. So they have hundreds and hundreds and hundreds of radiocarbon dates.

• 
  Pieces of organic matter they're able to date to provide some sort of age models, you know, for each section of your core, you know exactly how old it is.

• This is a real problem for what I do. Radiocarbon dating doesn't work for things that are 16,000,000 years old. There's no carbon 14 left in those bars. Not really. It's all decayed away. There's no way to reasonably measure the remaining c 14.

• What's been really exciting the last, really, ten years is some of the colleagues I worked with, like, say at Boise State, they've been able to refine other methods that are getting really, really precise.

• A real not a especially new method to date uranium to date zircons, little minerals that we find in some of those ashes that are interspersed in these rocks, but they're getting really, really precise. So with several of the dates that we use for our age models, we're getting an error bar plus or minus 10,000.

• The best one I've seen is like plus or minus 7,000 years.

Conclusion on Vegetation and the Fossil Records

• Ecosystems respond differently depending on the periods of geologic time.

• An uncomfortable thought of the research.

Findings

• It turns out to be 10,000,000 years younger than previously thought.

Local Findings and Concluding thoughts

• These results go into the regional story, thinking about where you have some plants finally going extinct, how things were hanging on until the bitter end.

• This place, the Michelle flora, is about 5 million years between 6 and 4, really, where we have a lot of bizarre plants hanging on the Northwest.